<wicket:extend xmlns:wicket="http://www.w3.org/1999/xhtml">
    <div wicket:id="filter">
        <label wicket:id="classLabel"></label>
        <select wicket:id="class"></select>
        <label wicket:id="documentLabel"></label>
        <select wicket:id="document"></select>
    </div>
</wicket:extend>